Fix build error for missing assembly attribute AllowPartiallyTrustedCallers
Fix build error for missing assembly attribute AllowPartiallyTrustedCallers

plutoo/protobuf-csharp-port,evgenekov/protobuf-csharp-port,plutoo/protobuf-csharp-port,plutoo/protobuf-csharp-port,evgenekov/protobuf-csharp-port,evgenekov/protobuf-csharp-port,happydpc/protobuf-csharp-port,happydpc/protobuf-csharp-port,happydpc/protobuf-csharp-port,evgenekov/protobuf-csharp-port,happydpc/protobuf-csharp-port,plutoo/protobuf-csharp-port